Overview of Web Services XML

In a distributed environment, applications might be created on different platforms by using different programming languages. Consider a scenario in which you need to access the functionality of an application that was created using Visual Basic .NET from a client application that is present on a computer running in the Unix environment.

In this case, you can create a Web service containing Web methods that allow you to access the functionality of the Visual Basic .NET application from an application running on a Unix based system. This allows you to integrate applications that were created and deployed on heterogeneous platforms.

Defining Web Services

A Web service is a new technology that you can use to create platform-independent applications. You can develop a Web service by using languages and platforms that adhere to a standard set of technologies. Therefore, using Web services, it is possible to access the functionality of an application that was created using Visual Basic .NET from a computer running on Unix, as we discussed in the previous example.

A Web service is an application that exposes functionality coded in an application to several applications. To do this, you need to invoke a Web service from an application called the Web service client application. In addition, the application that hosts the Web service is called the Web service provider application.

Accessing Web Services

To access the functionality that a Web service provides, a Web service client application needs to invoke the Web service by using its URL.

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A Web service can invoke another Web service as well. In this case, them Web service that sends a request for another Web service is the Web service client application. Suppose you created a Web service to validate the details of the credit card as entered by a user.

This Web service accepts the details, such as the name of the credit card holder and the credit card number. Based on this information, the details of the user, such as the credit card number, the expiration date of the credit card, and thecredit amount available for the specified credit card, are validated. You can name this Web service Credit_Details.

After introducing you to the basics of a Web service, we will discuss the architecture of a Web service. Understanding the architecture of a Web service will enable you to understand how a Web service works.